The present invention relates generally to traffic preemption systems and more specifically to a preemption system in which intersection preemption is handled by a centralized control facility. The present invention is related to U.S. patent application Ser. No. 10/811,075, the disclosure of which is incorporated herein by reference in its entirety
Traffic signals are typically determined by an intersection controller. Information is often communicated between intersection controllers and a centralized traffic management center via a fixed or wireless network. The network can be used to coordinate the timing of signals generated by various intersection controllers and to receive diagnostic information from intersection controllers.
Preemption systems are widely used to provide transit and emergency vehicles with the capability of disrupting a regular sequence of traffic signals in order to provide right of way through an intersection. Preemption systems can decrease the time taken for emergency vehicles to reach the scene of an accident/incident and/or ensure a greater likelihood of a transit vehicle maintaining its schedule. Preemption systems can use a variety of techniques to inform intersections that a preempting vehicle is approaching an intersection. Some systems use direct communication techniques such as optical or audio signals. Other systems locate the position of the preempting vehicle and communicate this information to intersection controllers via a wireless network. The intersection controller can then determine whether to preempt the traffic signals of the intersection and the timing of the preemption. A positioning system such as the global positioning system (GPS) can be used to estimate the position of a preempting vehicle. The accuracy with which the position of a vehicle is estimated can also be improved using map matching techniques.
Fleet management systems are commonly used to track the location of vehicles and provide diagnostic information to a centralized fleet management center. Fleet management systems can be useful in determining the location of resources and identifying vehicles that require maintenance before problems with the vehicle are manifest. Fleet management systems can also use GPS receivers to estimate vehicle position. This information in addition to onboard diagnostic information can then be transmitted to a control center via a wireless network.